Cytokine gene expression profiles in peripheral blood mononuclear cells from Neospora caninum naturally infected dams throughout gestation

Modulation of Bovine Endometrial Cell Receptors and Signaling Pathways as a Nanotherapeutic Exploration against Dairy Cow Postpartum Endometritis

Simple Summary

The provision of updated information on the molecular pathogenesis of bovine endometritis with host-pathogen interactions and the possibility of exploring the cellular sensors mechanism in a nanotechnology-based drug delivery system against persistent endometritis were reported in this review. The mechanism of Gram-negative bacteria and their ligands has been vividly explored, with the paucity of research detail on Gram-positive bacteria in bovine endometritis. The function of cell receptors, biomolecules proteins, and sensors were reportedly essential in transferring signals into cell signaling pathways to induce immuno-inflammatory responses by elevating pro-inflammatory cytokines. Therefore, understanding endometrial cellular components and signaling mechanisms across pathogenesis are essential for nanotherapeutic exploration against bovine endometritis. The nanotherapeutic discovery that could inhibit infectious signals at the various cell receptors and signal transduction levels, interfering with transcription factors activation and pro-inflammatory cytokines and gene expression, significantly halts endometritis.

Abstract

In order to control and prevent bovine endometritis, there is a need to understand the molecular pathogenesis of the infectious disease. Bovine endometrium is usually invaded by a massive mobilization of microorganisms, especially bacteria, during postpartum dairy cows. Several reports have implicated the Gram-negative bacteria in the pathogenesis of bovine endometritis, with information dearth on the potentials of Gram-positive bacteria and their endotoxins. The invasive bacteria and their ligands pass through cellular receptors such as TLRs, NLRs, and biomolecular proteins of cells activate the specific receptors, which spontaneously stimulates cellular signaling pathways like MAPK, NF-kB and sequentially triggers upregulation of pro-inflammatory cytokines. The cascade of inflammatory induction involves a dual signaling pathway; the transcription factor NF-κB is released from its inhibitory molecule and can bind to various inflammatory genes promoter. The MAPK pathways are concomitantly activated, leading to specific phosphorylation of the NF-κB. The provision of detailed information on the molecular pathomechanism of bovine endometritis with the interaction between host endometrial cells and invasive bacteria in this review would widen the gap of exploring the potential of receptors and signal transduction pathways in nanotechnology-based drug delivery system. The nanotherapeutic discovery of endometrial cell receptors, signal transduction pathway, and cell biomolecules inhibitors could be developed for strategic inhibition of infectious signals at the various cell receptors and signal transduction levels, interfering on transcription factors activation and pro-inflammatory cytokines and genes expression, which may significantly protect endometrium against postpartum microbial invasion.

From Signaling Pathways to Distinct Immune Responses: Key Factors for Establishing or Combating Neospora caninum Infection in Different Susceptible Hosts

: Neospora caninum is an intracellular protozoan parasite affecting numerous animal species. It induces significant economic losses because of abortion and neonatal abnormalities in cattle. In case of infection, the parasite secretes numerous arsenals to establish a successful infection in the host cell. In the same context but for a different purpose, the host resorts to different strategies to eliminate the invading parasite. During this battle, numerous key factors from both parasite and host sides are produced and interact for the maintaining and vanishing of the infection, respectively. Although several reviews have highlighted the role of different compartments of the immune system against N. caninum infection, each one of them has mostly targeted specific points related to the immune component and animal host. Thus, in the current review, we will focus on effector molecules derived from the host cell or the parasite using a comprehensive survey method from previous reports. According to our knowledge, this is the first review that highlights and discusses immune response at the host cell-parasite molecular interface against N. caninum infection in different susceptible hosts.

Antibody and cytokine response to Cystoisospora suis infections in immune-competent young pigs

Background

To date, investigations on the immune response to Cystoisospora suis infections focused on suckling piglets, the age group clinically most affected. Actively immunizing piglets is unfeasible due to their immature immune system and the typically early infection in the first days after birth. Therefore, understanding and possibly enhancing the immune response of immune-competent animals is the prerequisite to develop a passive immunization strategy for piglets which currently rely on very limited treatment options.

Methods

To investigate antibody and cytokine responses of immune-competent animals and the impact of the oral immunization protocol on their immune response, growers with unknown previous exposure to C. suis (10–11 weeks-old) were infected one or three times with different doses (600 and 6000 or 200 and 2000, respectively) of C. suis oocysts, and compared to uninfected controls. Oocyst excretion was evaluated, and blood and intestinal mucus antibody titers were determined by IFAT. Systemic production of Th1, Th2, inflammatory and regulatory cytokines was determined in different immune compartments at mRNA and (after stimulation with a recombinant merozoite-protein) at protein level by PCR and multiplex fluorescent immunoassay, respectively.

Results

Infection generated significantly increased serum IgA and IgG levels against C. suis sporozoites and merozoites, irrespective of infection mode, with IgG against merozoites showing the strongest increase. No clinical signs and only occasional excretion were observed. The systemic cytokine response to C. suis was only weak. Nonetheless, in white blood cells, IL-4, IL-6 and IL-10 mRNA-levels significantly increased after infection, whereas IFN-ɣ, IL-2 and TGF-β expression tended to decrease. In mesenteric lymph nodes (MLN), IL-10 and TNF-α levels were elevated while splenic cytokine expression was unaltered upon infection. Stimulated MLN-derived lymphocytes from infected pigs produced slightly more IL-12 and less IFN-α than controls.

Conclusions

An infection and a subsequent systemic immune response can be induced in immune-competent animals by all evaluated infection models and growers can be used as models to mimic sow immunizations. The immune response to C. suis, although mild and with considerable variation in cytokine expression, was characterized by a Th2-associated and regulatory cytokine profile and antibody production. However, none of the parameters clearly stood out as a potential marker associated with protection. Antibody titers were significantly positively related with oocyst excretion and might thus serve as correlates for parasite replication or severity of infection.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2974-6) contains supplementary material, which is available to authorized users.

Immune response in bovine neosporosis: Protection or contribution to the pathogenesis of abortion

Neospora caninum is a protozoan parasite with a preference for cattle and dogs as hosts. When N. caninum infection occurs in cattle it induces abortion, bovine neosporosis being a main cause of abortion worldwide. In dairy cattle, the economic burden of neosporosis-associated abortion is so great that it might results in closure of a farm. However, not all infected cows abort and it is not yet understood why this occurs. At present there is no effective treatment or vaccine. This review provides insights on how immune response against the parasite determines protection or contribution to abortion. Aspects on markers of risk of abortion are also discussed. Humoral immune responses are not protective against N. caninum but seropositivity and antibody level can be good markers for a diagnosis of bovine neosporosis and its associated abortion risk. In addition, humoral mechanisms against N. caninum infection and abortion differ in pure-breed and cross-breed pregnant dairy and beef cattle. Concentrations of Pregnancy Associated glycoprotein -2 (PAG-2) can also be used to predict abortion. A partially protective immune response encompasses increased IFN-γ expression, which has to be counterbalanced by other cytokines such as IL-12 and IL-10, especially towards the end of pregnancy. Although IFN-γ is required to limit parasite proliferation a critical threshold of the IFN-γ response is also required to limit adverse effects on pregnancy. In clinical terms, it may be stated that IFN-γ production and cross-breed pregnancy can protect Neospora-infected dairy cows against abortion.

NLRP3 inflammasome activation in murine macrophages caused by Neospora caninum infection

Background

Neospora caninum is an intracellular parasite that causes significant economic losses in cattle industry. Understanding the host resistance mechanisms in the innate immune response to neosporosis could facilitate the exploration of approaches for controlling N. caninum infection. The NLR inflammasome is a multiprotein platform in the cell cytoplasm and plays critical roles in the host response against microbes.

Methods

Neospora caninum-infected wild-type (WT) macrophages and Nlrp3^−/− macrophages, and inhibitory approaches were used to investigate inflammasome activation and its role in N. caninum infection. Inflammasome RT Profiler PCR Arrays were used to identify the primary genes involved in N. caninum infection. The expression of the sensor protein NLRP3, processing of caspase-1, secretion of IL-1β and cell death were detected. Neospora caninum replication in macrophages was also assessed.

Results

Many NLR molecules participated in the recognition of N. caninum, especially the sensor protein NLRP3, and further study revealed that the NLRP3 distribution became punctate in the cell cytoplasm, which facilitated inflammasome activation. Inflammasome activation-mediated caspase-1 processing and IL-1β cleavage in response to N. caninum infection were observed and were correlated with the time of infection and number of infecting parasites. LDH-related cell death was also observed, and this death was regarded as beneficial for the clearance of N. caninum. Treatment of N. caninum-infected macrophages with caspase-1, pan-caspase and NLRP3 inhibitors led to the impaired release of active IL-1β and a failure to restrict parasite replication. And Neospora caninum infected peritoneal macrophages from Nlrp3-deficient mice displayed greatly decreased release of active IL-1β and the failure of caspase-1 cleavage.

Conclusions

The NLRP3 inflammasome can be activated in N. caninum-infected macrophages, and plays a protective role in the host response to control N. caninum.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2197-2) contains supplementary material, which is available to authorized users.

Cytokine gene expression in aborting and non-aborting dams and in their foetuses after experimental infection with Neospora caninum at 110 days of gestation

Neospora caninum is a major cause of abortion in cattle. However, it is not known why not all infected animals abort. In this study, Th1 (IFN-γ), Th2 (IL4) and T reg (IL-10) cytokine gene expression was examined by real time PCR using the TaqMan approach in all of these dams and their foetuses after experimental infection with the isolate Nc-Spain7 at 110 days of pregnancy and euthanasia 6 weeks after infection. In prior published work, foetal death was observed in three of six infected dams and transplacental infection in all the 6 infected foetuses. In the spleen of the dams, IL-4 expression was down-regulated in dams with aborted/non viable foetuses compared to both uninfected dams (controls, n=3) and infected dams with live fetuses at euthanasia. In the lymph nodes draining the placenta, up-regulated expression of IL-4 was observed in infected dams with live foetuses compared to control dams. In the placenta, infected dams with live foetuses had significantly up-regulated IFN-γ in both caruncle and cotyledon and up-regulated IL-10 in cotyledon compared to control dams. Infected live foetuses showed up-regulated expression of IFN-γ and IL-10 in foetal spleen, and showed downregulated expression of IL-4 in the thymus compared to control uninfected foetuses. Expression of any cytokine in the thymus was significantly lower compared to the levels observed in foetal spleen. The results indicate an up-regulated expression of Th1, Th2 and Treg in infected dams with live foetuses and in their foetuses. On the other hand, down-regulation of Th2 immune responses and Treg cytokines were observed in infected dams which had aborted or had non-viable foetuses at euthanasia, suggesting an immunological recovery of cytokine gene expression levels in dams a few weeks after an abortion occurred.

Markers related to the diagnosis and to the risk of abortion in bovine neosporosis

Bovine neosporosis has emerged as a main cause of abortion in cattle worldwide. An important question to understand the disease is why not all infected cows abort. In the present review we summarize the knowledge on markers related to the diagnosis and more importantly to the risk of abortion in the infected cow. Markers considered herein include those based on specific antibodies, antibody titers and antibody subtypes, cellular immunological markers, hormones and other proteins related to gestation. The identification of parasite molecules that are specifically identified in the aborting cows might help to understand the mechanism of parasite-associated abortion and control the disease.

Effects of crossbreeding on endocrine patterns determined in pregnant beef/dairy cows naturally infected with Neospora caninum

Neospora caninum is an intracellular coccidian parasite causing abortion worldwide in dairy cattle. Studies have shown that N caninum infection modifies endocrine patterns and that beef cows or cows with a crossbreed pregnancy, especially for a greater maternal-paternal genetic distance, show a reduced risk of abortion when naturally infected compared with pure-breed Holstein Friesian (HF) pregnancies. This study examined the effects of crossbreeding on plasma progesterone (P4), pregnancy-associated glycoprotein (PAG)-1 and -2, and prolactin patterns produced during gestation in N caninum-infected beef/dairy cows. We analyzed 74 pregnancies in nonaborting cows carrying a single fetus established in 26 lactating HF cows bred with Holstein bulls (H-H), 13 HF cows bred with Limousin bulls (H-L), 12 HF cows used as recipients of transferred in vivo-produced frozen-thawed Rubia Gallega (beef breed; RG) embryos (H-RG-ET), and 23 RG suckling cows bred with RG bulls (RG-RG). Of the cows, 29 (39%) were seropositive for N caninum. Blood samples for hormone and placental protein determinations were collected on Days 30, 60, 90, 120, 150, and 180 of gestation. Procedures of repeated measures analysis of variance throughout gestation revealed higher PAG-1 levels in the H-L and H-RG-ET groups compared with H-H and RG-RG. Higher prolactin levels were detected in RG-RG than in the remaining groups. N caninum seropositivity and fetal genotype had a significant effect on PAG-2 concentrations, such that highest levels of PAG-2 occurred in RG-RG seropositive cows and lowest in H-H seropositive cows, whereas Neospora-seropositive cows showed lower P4 concentrations than their seronegative partners. In conclusion, chronic N caninum infection modifies endocrine patterns of PAG-2 and P4 during pregnancy, whereas PAG-1 and prolactin concentrations are affected by breed and fetal genotype, irrespective of Neospora infection status.

Maternal and fetal immune response patterns in heifers experimentally infected with Neospora caninum in the second trimester of pregnancy--a descriptive study

Fetal and maternal immune responses 3, 6 and 9 weeks post infection (wpi) were investigated in cows experimentally infected with Neospora caninum on day 110 of gestation. Descriptive analysis showed that the fetuses had lower percentages of spleen T cell subpopulations (CD3+, CD4+ and CD8+) at 6 wpi compared to 3 wpi and/or 9 wpi, with the lowest percentages observed in a dead fetus found upon euthanasia at that time. Increased expression of most cytokines over levels recorded at 3 and 9 wpi were found in fetuses that were alive at 6 wpi. Up-regulated Th1, Th2 and Treg expression was also observed at 6 wpi in the spleen and in the lymph nodes draining the placenta of the cows. At the placental level, while most cytokines were down-regulated from 6 wpi, up-regulation of IL-4 expression was observed at 6 wpi in the caruncle. Our results suggest that the immune response at 6 wpi was crucial for fetal survival in this model of bovine neosporosis.

Neospora caninum infection during early pregnancy in cattle: how the isolate influences infection dynamics, clinical outcome and peripheral and local immune responses

This work studies the influence of Neospora caninum intra-species diversity on abortion outcome, infection dynamics in terms of parasite dissemination and peripheral-local immune responses in pregnant cattle. Animals were intravenously inoculated at day 70 of pregnancy with 10⁷ tachyzoites of two isolates showing marked differences in virulence in vitro and in pregnant mouse models: Nc-Spain7, a high virulence isolate, and Nc-Spain8, a low-to-moderate virulence isolate. After inoculation, pregnancy was monitored, and dams were culled when foetal death was detected. Foetal mortality occurred in all infected heifers between days 24 and 49 post-infection (pi), however, it was detected sooner in Nc-Spain7-infected animals (median day = 34) than those inoculated with Nc-Spain8 (median day = 41) with a trend towards significance (P < 0.11). Similar histological lesions were observed in placentomes and in most of the foetuses from the two infected groups. However, parasites were more frequently detected in the placenta and foetuses by PCR and in the foetal brain by immunohistochemistry in Nc-Spain7-infected animals. Specific antibodies were detected starting at day 13 post-infection in all infected cattle, with higher IgG levels in Nc-Spain7-infected group. IFN-γ and IL-4 profiles also varied between infected groups in PBMC stimulation assays. Infected animals showed significant increases in their cytokine mRNA levels (IFN-γ, IL-4, IL-10, IL-12p40 and TNF-α) in the caruncle at time of foetal death. Differences between the infected groups were also observed for cytokine profiles. These results demonstrate the influence of the N. caninum isolate on foetal death outcome, infection dynamics and immune responses in cattle.

Gamma interferon production and plasma concentrations of pregnancy-associated glycoproteins 1 and 2 in gestating dairy cows naturally infected with Neospora caninum

Gamma interferon (IFN-γ) production and cross-breed pregnancy have been attributed a role in protecting dairy cows infected with Neospora caninum against abortion. Plasma levels of pregnancy-associated glycoproteins-1 (PAG-1) are a marker of placental/foetal well-being and of PAG-2 is an abortion risk indicator in chronically N. caninum-infected animals. The present study examines, in cross-breed pregnancies, interactions between IFN-γ production and levels of PAG-1 and PAG-2 in non-aborting naturally Neospora-infected dairy cows. Data were obtained from 60 pregnant Holstein-Friesian cows: 44 Neospora-seropositive and 16 Neospora-seronegative; 12 became pregnant using Holstein-Friesian semen and 48 using Limousin semen. Blood samples were collected on Days 40, 90, 120, 150, 180 and 210 of gestation. Gamma interferon was only detected in the plasma of nine of the 44 Neospora-seropositive cows, all of them became pregnant using Limousin semen. Through GLM procedures, in cows inseminated with Limousin semen and Neospora-seropositive cows showing no IFN-γ production, PAG-1 concentrations were high and increased throughout gestation compared to the levels detected in cows inseminated with Holstein-Friesian semen and Neospora-seropositive cows producing IFN-γ, respectively. In Neospora-seronegative cows and in Neospora-seropositive cows showing no IFN-γ production, significantly increased PAG-2 concentrations were observed on gestation Day 120. Our findings indicate that IFN-γ production correlates negatively and the production of antibodies against N. caninum is uncorrelated with plasma PAG concentrations during gestation in Neospora-infected dairy cows. Accordingly, IFN-γ production could be linked to the transplacental migration of tachyzoites, which may cause a reduction in PAG levels.

Modulation of maternal immune system during pregnancy in the cow

There is a molecular crosstalk between the trophoblast and maternal immune cells of bovine endometrium. The uterine cells are able to secrete cytokine/chemokines to either induce a suppressive environment for establishment of the pregnancy or to recruit immune cells to the endometrium to fight infections. Despite morphological differences between women and cows, mechanisms for immune tolerance during pregnancy seem to be conserved. Mechanisms for uterine immunesuppression in the cow include: reduced expression of major histocompatability proteins by the trophoblast; recruitment of macrophages to the pregnant endometrium; and modulation of immune-related genes in response to the presence of the conceptus. Recently, an eGFP transgenic cloned embryo model developed by our group showed that there is modulation of foetal proteins expressed at the site of syncytium formation, suggesting that foetal cell can regulate not only by the secretion of specific factors such as interferon-tau, but also by regulating their own protein expression to avoid excessive maternal recognition by the local immune system. Furthermore, foetal DNA can be detected in the maternal circulation; this may reflect the occurrence of an invasion of trophoblast cells and/or their fragment beyond the uterine basement membrane in the cow. In fact, the newly description of exosome release by the trophoblast cell suggests that could be a new fashion of maternal-foetal communication at the placental barrier. Additionally, recent global transcriptome studies on bovine endometrium suggested that the immune system is aware, from an immunological point of view, of the presence of the foetus in the cow during early pregnancy.

Production of a bovine IL-12p40 probe and application using in situ hybridization on ruminant fixed tissues

Pro-inflammatory cytokines (particularly IL-12) are important for initiating protective T helper 1 (Th1)-type immune responses and hence vital for combating intracellular infections and tumours. In situ hybridization (ISH) provides a powerful diagnostic tool allowing the identification and localization of cells producing these mediators in fixed tissues. The objective of this work was to produce a bovine IL-12p40 probe that allows detection of IL-12p40 mRNA in fixed tissues from different ruminant species. The RNA probe sequence is 447bp in length and from a region with high cross-species-sequence homology (>97.3% homology) to the ovine, cervine, caprine and bubaline IL-12p40 genes. ISH was carried out on paraformaldehyde fixed tissues collected from cattle, sheep and goats. The probe was efficient in identifying IL-12p40 expressing cells in fixed tissues from all these species. In conclusion, the IL-12p40 probe was efficient in identifying and localizing cells that express IL-12p40, and provides a good immuno-diagnostic technique to characterize immune responses in fixed tissues.